1. Field of the invention
The present invention relates to a shift range switching control apparatus (or a gear shift switching control apparatus) capable of selecting the current gear in a vehicle automatic transmission system using an actuator and of detecting the driver's operation of the gear shift lever of the vehicle.
2. Description of the Related Art
Various types of a shift range switching control apparatus (or a gear shift switching control apparatus) have been known and used in vehicles. The shift range switching control apparatus switches the shift range (or drive range) of the automatic transmission of a vehicle in response to the driver's operation of the gear shift lever such as a gear stick, a gear selector, a selection lever, and a shift stick. For example, the shift range switching control apparatus has a shift-by-wire type using a direct current (DC) motor as an actuator. When electrically detecting the gear position of the gear shift lever operated by the vehicle driver, the shift range switching control apparatus of a shift-by-wire type instructs the DC motor as an actuator to switch the shift range of the automatic transmission in response to the detected gear position.
Because the shift range switching control apparatus of a shift-by-wire type does not need to mechanically engage the gear shift lever with the shift range for the automatic transmission of the conventional mechanisms and methods capable of directly switching the shift range of the automatic transmission using the gear shift lever directly operated by the vehicle driver, the apparatus of a shift-by-wire type has an advantage which does not limit the location for mounting the shift range switching control apparatus onto the vehicle. For example, related art documents, Japanese patent laid open publications No. JP 2000-170905, and JP 2002-254941 have disclosed the advantage of the shift range switching control apparatus of such a type.
The operation unit, namely, the gear shift lever in the shift range switching control apparatus of the shift-by-wire type has two types, the momentary type (an automatic reset type) and the alternate type (as a manual reset type, or a position retaining type).
The operation unit (the gear shift lever) of the momentary type is operated from its original position to the operation position while the vehicle driver operates, namely, applies a force to the gear shift lever. When the vehicle driver releases the operation unit of the momentary type, the operation unit is automatically returned to its original position. For example, Japanese patent laid open publication No. JP 2002-254941 as a related art technique has disclosed such a mechanism of the operation unit of the momentary type.
On the other hand, the operation unit (the gear shift lever) of the alternate type is operated from the current position to another gear position when the vehicle driver operates, namely, applies a force to the gear shift lever. The operation unit of the alternate type is maintained at its current position even if the vehicle driver releases the operation unit. The operation unit of the alternate type is also used in conventional shift range switching control apparatus.
A related art technique, for example, Japanese patent laid open publication No. JP 2002-254941 has proposed the shift range switching control apparatus of the shift-by-wire type equipped with a CCD camera. This CCD camera monitors the driver's switching operation of the gear shift lever. The system including the shift range switching control apparatus system ignores the operation of the gear shift lever when the gear shift lever is operated contrary to the vehicle driver's will, for example, when the gear shift lever is operated by a vehicle passenger other than the vehicle driver.
Still further, there is another related art technique to ignore the driver's operation of the gear shift lever to switch to the drive (D) position or the reverse (R) position when the vehicle driver does not depress or press down the brake pedal.
The above related art techniques is capable of detecting an obvious error operation contrary to the driver's will and also detecting an obvious error operation caused by combining various driver's operations. However, the shift range switching control apparatus of the above related art techniques cannot detect any driver's incomplete operation (or driver's half-finished operation).
For example, following cases (1) to (3) can be considered as the driver's incomplete operations:
(1) The vehicle driver releases the gear shift lever of the momentary type before the gear shift lever completely reaches a target gear position;
(2) The vehicle driver releases the gear shift lever of the momentary type before the shift range switching control apparatus detects that the gear shift lever reaches the target gear position after the gear shift lever reaches the target gear position; and(3) The vehicle driver releases the gear shift lever of the alternate type on the way to the original position of the gear shift lever after the gear shift lever reaches the target gear position.
In the latter case (3), the shift range switching control apparatus does not detect the operation of the gear shift lever because the gear shift lever is left at an unstable position other than the effective gear positions.
When the driver's incomplete operations (1) to (3) described above occur, the vehicle driver thinks that he has correctly completed the operation of the gear shift lever, but the shift range switching control apparatus does not detect that the gear shift lever has reached the target gear position, and, as a result, does not switch the current gear position to the target gear position. This would cause the driver's vehicle to move in an incorrect direction such as a dangerous direction, and an accident would happen.